Liquid oxygen pump



Aug. 24, 19 48. w, b5 BAUFRE 2,447,741

LIQUIDOXYGEN run? Filed Dec. 12,1944

Patented Aug. 24,1948

UNITED srA'res PATENT orrica 1 li u nifirium. 1

1: cum ins-1)- This invention relates to improvements in pumps forwithdrawing oxygen in liquid form from rectifying columns of plantsextracting oxygen from atmospheric air by liquefaction andrectification. The liquid oxygen may be discharged against high pressuresuchas is customary for storage of gaseous oxygen in cylinders at roomtemperature. For storage as gas eous oxygen, the liquid oxygen may bevaporized under the discharge pressure and warmed to room temperature toeffect cooling of warm air to be subsequently liquefied as proposed byM. von Recklinghausen in U. S. Patent No. 1,394,- 955, issued in 1921.-

The improved liquid oxygen pump described in this specification may alsobe used to increase the pressure of other liquefied gases before theirvaporization by transfer of latent heat from the gaseous fluid to theliquid whose pressure has been raised" as explained in various patentsto E. A. W. Jetleries and F. E. Norton, see their U. S. Patents No.1,264,807 and 1,264,845 issued in 1918.

Thus, the idea is not new to use a liquid oxygen pump to withdraw oxygenin liquid form from a rectifying column and return the liquid underincreased pressure in heattransfer with atmospheric air to liquei'y it,the liquid oxygen being vaporized and warmed to room temperature. Theadvantages of so doing were pointed out by von Recklinghausen. Thus,compression of the gaseous oxygen in order to store it in cylinders ortanks is eliminated, whereby great economy is affected because the workto pump liquid oxygen against a pressure difference is much less thanthe work to compress the same mass of gaseous oxygen between the sametwo pressures. Furthermore, the possibility of introducing impuritiessuch as water into the oxygen is greatly reduced if not eliminated.

The present invention comprises improvements in the construction andoperation of liquid oxygenpumps to meet satisfactorily the conditions'towhich such pumps are subjected. Thus, the very low temperature of liquidoxygen, below minus 119 centigrade, necessitates imbedding the cylinderof a liquid oxygen pump within thick insulation to reduce heat leak fromthe surroundings at room temperature into the liquid oxygen. As the pumpplunger is operated by mechanism at room temperature outside theinsulation, an operating rod must extend from the mechanism at roomtemperature through the insulation to the plunger within the cylinder atvery low temperature. One object of the present invention is to reduceheat leakfrom the surroundings along the operating rod into the liquidoxygen pumped.

The operating rod extends to the plunger in the cylinder where theliquid oxygen is under high pressure and some form of packing must beused around the plunger to hold the liquid oxygen while permittingmovement oi the plunger. An-

other obiect of the invention is to recover any liquid oxygen leakingpast the packing and to prevent loss of liquid oxygen along theoperating rod.

The liquid oxygen 'to be pumped may contain impurities such assolidified carbon dioxide which would adversely ailectoperationof thepump. A further-object of the invention is to reduce or eliminate suchimpurities.

A liquid oxygen pump might-fail to operate by becoming vapor bound dueto vaporization of liquid by heat produced by friction or leaking intothe pump cylinder from the surroundings. v A further object of theinvention is to reduce the danger of vapor binding.

The rate of pumping of liquid oxygen should be 7 adjustable inaccordance with demands for oxygen and the purity of oxygen desired. The

pressure pumped against should be limi'tedto a safe value. Anotherobject of the invention is of pumping liquid oxygen, for automaticallyreducing the rate of pumping to prevent excess pressure, and forautomatically restoring the higher rate of pumping when the pressuredrops to a normal value.

Other objects of the invention are to indicate the rate of oxygenproduction at any time and to sum up the total oxygen production duringany period. V

The foregoing objects together with such additional and subsidiaryadvantages as may hereinafter appear. or are incident to the invention,are realized by the novel apparatus described herein and shown inpreferred form-on the drawings as follows:

Figure 1 is a cross-section of the new and improved liquid oxygen pumpwith the pump cylinder deeply imbedded in insulation and with a plungerand operating rod.

Referring to Figure 1, pump cylinder 1 is leaking into vessel 2.

5. Pipe 4 is connected to container 6 at a point above the point ofconnection of pipe 2 and preier-ably above the liquid level withincontainer 5. Pipe 4 is connected to vessel 2 near its highest part so asto discharge all vapor formed by Liquid oxygen to be pumped flows fromcontainer 5 through filter 8 and pipe 3 to vessel 2.

Any impurities such as solid carbon dioxide in the liquid oxygen incontainer 5 are removed by filter 6 before the liquid oxygen reachesvessel 2. If these impurities were not strained out of the liquid oxygenbefore it reached the pump, these impurities might adversely affectoperation of the pump by sticking to valves to prevent their functioningor to plunger and cylinder walls to augment frictional resistances.

Vessel 2 is located at some distance below container! in order thatliquid oxygen within vessel 2 will be under greater hydrostatic pressurethan in container 5 where the pressure will usually correspond to theboiling temperature of the liquid oxygen. In container 5, any absorptionof heat would therefore produce vaporization of the liquid oxygen. Invessel 2, some heat can be absorbed without vaporlkation of the liquidoxygen because it is first necessary to raise the liquid to a highertemperature before it will boil under the greater hydrostatic pressuretherein.

Suction opening I to pump cylinder I is located near the lowest part ofvessel 2 so that the coldest liquid oxygen will be sucked into the pump.

heat

. annular clearance space between rod 22, tube II The coldest liquidoxygen will tend to flow to the lowest part of vessel 2 by reason of itsgreater density relative to surrounding liquid. This tendency isfacilitated by connecting pipe 3 to vessel 2 as shown so as to favorflow of entering coldliquid to the bottom of vessel 2 along itsprotected side. Pipe 2 might be connected to the lowest point of vessel2; but the connection shown will usually be about as effective and ispreferable to a longer pipe with more bends. Drain pipe 8 is connectedto the lowest point of vessel 2 for draining all liquid therefrom.

Cylinder I is part of or "is attached to cover 9 which is bolted toflange III on vessel 2. This construction enables pump cylinder I to bewithdrawn from vessel 2 for maintenance purposes way shown from valve l2through the wall of cyl-' inder I enables pipe I for discharge of liquidoxygen under high pressure, to be connected to cover 9.

Plunger I5 has reciprocating motion back and forth within cylinder I.Packing it around plunger I5 within cylinder I is provided to reduce ifnot prevent leakage of high pressure liquid oxygen along plunger I5during its inward forcing stroke. This packing is V-type leather whichhas been treated to remain flexible at very low temperature. It isarranged with the trough of the V towards the end of the plunger so thatthe leather will be pressed against cylinder wall and anism would becomecovered with frost from moisplunger by the high pressure of the liquidoxygen during the forcing stroke. Leather packing I! is held in place bygland II which is part of tube II extending through insulation I2 andbase plate 2.. At the outer end of tube II is a second leather packing2i around operating rod 22 attached to plunger II. Packing II is held inplace by gland nut 22.

Operating rod'22 does not fit tightly within tube It in order-to avoidfrictional resistance to its reciprocating motion. There is, therefore,an

and the two leather packings l6 and 2|. This clearance space isconnected at its lower end to the liquid oxygen space within vessel 2 byholes .through gland I1 and through the wall of cylinder I. An annularspace is formed between the bottom of a counterbore in cylinder I andthe lower end of gland II where its diameter is reduced to hold packingII in place. Holes through gland ll connect this annular space to theclearance space between rod 22 and tube I2. A hole through the cylinderwall connects the annular space to the space within vessel 2. Liquidoxygen atsuction pressure within vessel 2 can enter the clearance spacebetween rod 22. tube I8 and packings I and 2| through the holes to theannular space at the lower end of gland II.

More important, any liquid oxygen leaking along plunger II past packingI. cannot build up pressure in the clearance space between rod 22, tubell and packings l8 and 2 I, becausethis liquid oxygen will flow throughthe holes described into vessel 2 at suction pressure and be returned tocylinder I through suction opening I. Consequently, packing 2| at theouter end of tube II is always subjected to the low suction pressurewithin vessel 2.

Tube ll of this liquid oxygen pump is inclined upwards from cylinder Ito th operating mechanism outside insulation II. This is done in orderthat liquid oxygen will not flow from cylinder I along the clearancespace until it reaches packing 2i under normal conditions of leakage atpacking 2|. If tube II were horizontal or inclined downwards, liquidoxygen could flow along the clearance space between operating rod 22 andtube l8 until it reached the outer end of the tube where it would bevaporized in cooling this outer end to very low temperatures. Large lossof refrigeration would result and the operating mechture in surroundingatmospheric air. This frost would interfere with lubrication andoperation of the mechanism. By inclining tube It with an upward slant asshown in Figure 1, liquid oxygen never reaches the outer end of tube IIunder normal conditions.

There will always be some heat leak along tube It and rod 22 from theirouter ends exposed to room temperature to their inner ends subjected toliquid oxygen temperature. This heat will slowly vaporize any liquidoxygen within the clearance space between rod 22 and tube It. With onlyslight leakage past packing 2|, the clearance space will remain filledwith gas and liquid oxygen will remain at the lower end of the clearancespace. Oxygen gas in th clearance space will assume substantially thesame temperature gradi ent as rod 22 and tube II and will conduct verylittle heat along the clearance space.

In order to reduce conduction of heat along rod 22 and tube II, theseare made of material having low heat conductivity, preferably Monelmetal which also has strength and resistance to abrasion suitable forthis purpose. Operating rod 22 is made hollow to reduce thecross-sectional area for conduction of heat along the rod and tosecureample stiflness for the forcing stroke against high liquid oxygenpressure. At its inner end, operating rod 22 is screw-connected to solidplunger i3.

'At its outer end, operating rod 22-is coupled to 22 can havereciprocating motion in a straight line. Lever 25 is oscillated byconnecting rod 23 connecting lever pin 33 to crank pin 3!. Crank pin 3iis in crank arm 32 which is attached to and rotates with shaft 33mounted in bearings 33, see'Figure 2, supported by brackets on base -plate 23. Tube [3 is supported in base plate 23 so as to withstand thethrust oi plunger II during the forcing stroke. Base plate 23 is mountedon the casing'for insulation l3.

, Shaft 33 rotates in the direction of the arrow in Figure 1. The centerof shaft 33 is offset from a line through the center of pin 33 andparallel to operating rod 22. This is done to reduce sidewise pressureon operating rod 22 during the inward forcing stroke of plunger i3.During the outward.

suction stroke, larger angularity of connecting rod 29 is permissiblebecausethe forces involved are low. With crank arm 32 in the positionshown in Figure 1 at right angles to and pointing towards operating'rod22, a line passing through It is generall desirable to operate a plantat the maximumirate of ,,oxygen production until totalrequirements aremet. If cylinders or tanks are being charged with gaseous oxygen, thepressurepumpedagainst will continue to rise if the rate ofpumpingof'liquid oxygen is not checked.

Automatic means of so doing are shown in Figure .2. The controlmechanism of variable speed drive. 33 is connected by extended shaft 43to pressure device 3| on'oxygen discharge pipe 32. When the oxygendischarge pressure rises above any'set value, the excess pressure actsthrough device I and extended shaft 33 to cause variable speed drive 33to-rotate shaft 33 at a lower rotative oxygen pressure.

the center of pin 30 and parallel to rod-22 lies about halfway betweenthe centers of crank pin 3i and shaft 33.

Shaft 33 is driven by variable speed drive 35 direct connected toelectric motor "as shown in Figure 2. Variable speed drive 33 canrevolve at any rotative speed from zero to say 40. revolutions perminute with electric motor 33 running at constant rotative speed. Therotative speed of variable speed drive 33 is adjusted manually bycontrol handle 31 and is indicated on dial 33 l with micrometer drumattached to control handle 31 for accurate speed setting. Revolutioncounter 33 is attached to the end of shaft 33 to sum up the total numberof revolutions during ony given period.

Since the stroke of plunger II is fixed by the dimensions of theoperating mechanism, the plunger displacement remains the same duringeach revolution of shaft 33. That is, the same volume of liquid oxygenis sucked into and discharged from cylinder l during each revolution ofshaft 33 except as affected by slip which varies somewhat with operatingpressure and rotative speed. Approximately, dial "indicates therate ofpumping liquid oxygen at any instant and counter 33 sums up the amountof liquid oxygen pumped during an period of time.

The purity of oxygen produced by a plant for.

extracting oxygen from atmospheric air bylique faction and rectificationvaries with the rate at which oxygen is withdrawn therefrom. With theabove described means for accurately reproducing the rate at whichliquid oxygen is withdrawn from such a plant, it becomes possible toreproduce any desired purity of oxygen without loss of time in makingchemical analyses of the product. The plant can be set to operate at anyrate of oxygen production from a maximum rate corresponding to thelowest permissible purity to zero rate. Any

desired rate of production can be quickly obtained and then maintained.a

22' is firmly attached by hand nut 33.

speed, which decreases with increasing pressure until shaft 33 comes torest with no further rise in Device ll may be of any wellknown type inwhich pressure change'prod'uces mechanical movement. It may be locatedat any point a1ong ,the discharge conduit for the liquid oxygen pumped,preferably after the liquid has been vaporized and warmed to roomtemperature.

When gaseous oxygen is supplied to a system from which the oxygen iswithdrawn at a variable rate, device l'i will operate to reduce the rateof oxygen production when the pressure exceeds a set value and toincrease the rate again when the pressure drops. a

Operating rod22 is coupled to pin- 23 in lever 25 through detachable endpiece 43 to which rod End piece 43 fits-into hollow rod 22 so as to.take the thrust on the inward forcing stroke of plunger 15. Thisconstruction is employed in order that plunger l3 and operating rod 22can be entirely removed from tube l3; Hand nut 34 isflrst loosened. Thelever mechanism is dropped slightly as indicated in Figure '3. I canthen be withdrawn between pins 23 and 23 and the two bars of lever 25.-These two bars are spaced far enough apart to permit this to be done.

The whole levermechanism on base plate 20 is protected by cover 35 withhinged lid 46. This cover protects the mechanism from dust and grit andkeeps atmospheric moisture away from the outer ends of operating rod 22'and tube l3. Any slight leakage of dr oxygen gas past packing 2i willfill the space within cover 33 with dry gas.

' Hinged lid 33 can be raised as indicated in Figure air must be war-medabove room temperature .oc-

casionally to defrost them. .Warm dry air is used for this purpose. Byblowing this warmdry air through filter 3, pipe 3, vessel 2 and drainpipe 3, any solid carbon dioxide in filter 3 will be vaporized anddischarged from the system. Plunger i3 and rod 22 can then be withdrawnfor blowing the warm dry air through cylinder l and tube I3 pastpackings ii and 2| to defrost these packings. v

Ielaim:

1. Liquid oxygen pump including a vessel, a source of liquid oxygen, aninlet pipe connected to the source below the liquid level therein foradmitting liquid oxygen to the vessel. a cover for the vessel, acylinder attached to the cover and projecting into the vessel so as tobe surrounded Plunger l5 and operating rod 22 7 reduce heat leak intothe vessel from the surroundings, and an outlet pipe near the highestpart of the vessel connected to the source of liquid oxygen above theliquid level therein for continuously discharging oxygen vapor formed byheat leak into the vessel.

2. Liquid oxygen pump as in claim 1 wherein the suction opening into thecylinder is located near the lowest part of the vessel.

3. Liquid oxygen pump as in claim 1 including a discharge pipe forliquid oxygen attached to the cover of the vessel.

4. Liquid oxygen pump as in claim 1 wherein said vessel is located belowsaid source.

5. Liquid oxygen pump as in claim 1 including packing around theplunger, and a passage-way from the clearance space beyondthe packinginto the vessel, whereby liquid oxygen leaking past the packing isreturned into the vessel.

6. Liquid oxygen pump as in claim 1 wherein said vessel is located belowsaid source and a filter is'provided in said inlet pipe, for removingimpurities such as solid carbon dioxide from the liquid oxygen before itreaches said cylinder.

7. Liquid oxygen pump including a cylinder imbedded in insulation toreduce heat leak from the surroundings into the liquid oxygen, a tubeextending from the cylinder through the insulation, a reciprocatingplunger within the cylinder attached to an operating rod extendingthrough the tube, the reciprocating plunger having substantially thesame diameter as the operating rod which is smaller than the insidediameter of the tube, an oscillating lever composed of two bars spacedfarther apart than the diameter of the operating rod, means forconnecting the operating rod to the oscillating lever whereby theplunger is given reciprocating motion, within the cylinder, and meansfor disconnecting the operating rod from the oscillating lever wherebythe operating rod and plunger can be withdrawn from the cylinder andtube between the bars of the oscillating lever.

8. Liquid oxygen pump including a vessel imbedded in insulation toreduce heat leak into said vessel, a pump cylinder mounted within saidvessel, a source of liquid oxygen, a pipe connecting said source belowthe liquid level to said vessel, a second pipe connecting said sourceabove the liquid level to said vessel near its highest point, a tubeextending from the pump cylinder through the insulation, a reciprocatingplunger within the pump cylinder attached to an operating rod extendingthrough the tube, a packing around the operating rod within the tubenear its outer end, and a passageway from the clearance space betweenthe operating rod and the tube to the space within said vessel aroundsaid pump cylinder,'whereby liquid oxygen leaking past the reciprocatingplunger is returned to said vessel around said punjp cylinder, vaporizedoxygen is returned to said source, and the packing is subjected tosubstantially the same pressure as in said source.

9. Liquid oxygen pump including a cylinder imbedded in insulation toreduce heat leak from the surroundings into the liquid oxygen, a tubeextending from the cylinder through the insulation, a reciprocatingplunger within the cylinder attached to an operating rod extendingthrough the tube, a packing around the plunger within the cylinder heldin place by a gland which forms partof said tube and projects into acounterbore in said cylinder whereby an annular space is formed betweenthe gland and the bottom of the counterbore, a suction valve for flow ofliquid OXYIEII into said cylinder, and 8. passagewayd'rfim the clearancespace between the operating rod and the tube to the suction valve formedby holes through the gland and through the cylinder wall to saidannular. space, whereby liquid oxygen leaking past said packing isreturned to said suction valve.

10. Liquid oxygen pump including a cylinder imbedded. in insulation toreduce heat leak irom the surroundings into the liquid oxygen, a Monelmetal tube extending i'rom the insulation, and a reciprocating plungerwithin the cylinder attached to a Monel metal operating rod extendingthrough the tube to a mechanism outside the insulation.-

11. Liquid oxygen pump as in claim 10 wherein the operating rod ishollow to reduce heat leak along the rod.

' 12. Liquid oxygen pump including a cylinder imbedded in insulation toreduce heat leak from the surroundings into the liquid oxygen, a tubeextending from the cylinder through the insulation, a reciprocatingplunger within the cylinder attached to an operating rod extendingthrough the tube, a packing around the plunger within the cylinder, asecond packing around the operating rod within the tube near its outerend, the tube being inclined upward from the cylinder whereby the secondpacking is subjected to gaseous oxygen and any liquid oxygen within theclearance space between operating rod and tube the cylinder.

13. Liquid oxygen pump as in claim 12 including a suction valve foradmitting liquid oxygen into said cylinder and means for returning tosaid suction valve liquid oxygen leaking past the reciprocating plunger.

remains near 14. Liquid oxygen pump as in claim 12 including a sourcefrom which liquid oxygen is supplied to said cylinder and means forreturning to said source vapor formed by heat leak into oxygen liquidleaking past the reciprocating plunger.

15. Liquid oxygen pump including a cylinder imbedded in insulation toreduce heat leak from the surroundings into the liquid oxygen, a tubeextending from the cylinder through the insulation, a reciprocatingplunger within the cylinder attached to an operating rod extendingthrough the tube, a packing around the plunger .within the cylinder, 9.second packing around the operating rod within the tube and near itsouter end,

a suction valve for admitting liquid oxygen into the cylinder, a sourceof liquid oxygen, a space connected near its lowest point to saidsuctionvalve and near its highest point to said source, and a passagewayfrom said space to the clearance space between the operating rod and thetube whereby liquid oxygen leaking past the first packing is returned tosaid suction valve, vapor formed therefrom is returned to said source,and the second packing is subjected to the suction pressure.

16. Liquid oxygen pump including a cylinder imbedded in insulation toreduce heat leak from the surroundings into the liquid oxygen, a tubeextending from the cylinder through the insulation, a reciprocatingplunger within the cylinder I attached to an operating rod extendingthrough the tube, a source of liquid oxygen, 3, suctionvalve foradmitting liquid oxygen into said cylinder,

means for separating vapor formed by heat leak into liquid oxygenleaking past the plunger from the remaining liquid oxygen, means forreturning.

the vapor formed to the said source, and means the cylinder through forreturning the remaining liquid olyzen to the saidsuction valve. Numberfile of this patent: 10 1,330,781

UNITED sums PATENTS 4 Name Date Heylandt July 24, 1934 Mack Mar. 3, 1885Bong Dec. 28, 1909 Measinger Octg22, 1935 Hansen Aug. 11, 1942 Dana Aug.11, 1942 L smyhr et a]. Sept. 28, 1943

